Piezoelectric/electrostrictive device and method of manufacturing same

ABSTRACT

A pair of opposing thin plate sections, movable sections, and fixed sections for supporting the thin plate sections and the movable sections are provided on a ceramic substrate. After a wiring pattern and a gap or an insulating layer of cermet layer for filling the gap are formed on a ceramic substrate, these are sintered. After that, piezoelectric/electrostrictive layers and cermet electrode layers including a piezoelectric/electrostrictive material and a conductive material are alternately stacked in a comb like structure on the ceramic substrate. Accordingly, a piezoelectric/electrostrictive device having the piezoelectric/electrostrictive element in multilayer structure is obtained.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application is a division of U.S. application Ser. No.10/341,543, filed Jan. 13, 2003, the entirety of which is incorporatedherein by reference.

[0002] This application also claims the benefit of Japanese ApplicationNo. 2002-005289, filed Jan. 11, 2002, the entirety of which isincorporated herein by reference.

BACKGROUND OF THE INVENTION

[0003] 1. Field of the Invention

[0004] The present invention relates to a piezoelectric/electrostrictivedevice comprising a ceramic substrate and at least apiezoelectric/electrostrictive element stacked on the ceramic substrateby means of a film formation method, and more particularly to apiezoelectric/electrostrictive device comprising a plurality ofpiezoelectric/electrostrictive layers and a plurality of electrodelayers including a piezoelectric/electrostrictive material stackedalternately in a comb like structure on a ceramic substrate and to amethod for producing the same.

[0005] 2. Description of the Related Art

[0006] In a piezoelectric/electrostrictive device such as an actuatorelement and a sensor element including a piezoelectric/electrostrictivelayer, firstly, a wiring pattern, which is composed of one electrodelayer, is formed on a ceramic substrate by, printing for example.Secondly, the piezoelectric/electrostrictive layer is further formed onthe wiring pattern by printing to secure the wiring pattern and thepiezoelectric/electrostrictive layer to the ceramic substrate bysintering. After that, a wiring pattern, which is composed of the otherelectrode layer, is formed.

[0007] The piezoelectric/electrostrictive device is used as an actuatorelement in which an electric field is applied to thepiezoelectric/electrostrictive layer by supplying an electric signal tothe wiring pattern, and the piezoelectric/electrostrictive layer isconsequently displaced. Additionally, the piezoelectric/electrostrictivedevice can be used as a sensor element in which an electric signal,which is generated depending on a pressure applied to thepiezoelectric/electrostrictive layer, is extracted from the wiringpattern.

[0008] The piezoelectric/electrostrictive device as described aboveinvolves the following fear. That is, for example, the wiring pattern inthe lower layer undergoes any thermal shrinkage, and a part of thewiring pattern is evaporated when the piezoelectric/electrostrictivelayer is sintered. As a result, a lot of unnecessary pores appear in thewiring pattern and pores having large opening areas appear to decreasethe portion (conductive portion) which actually functions as theelectrode layer.

[0009] In such a situation, the area of the electrode layer issubstantially decreased. Therefore, the capacitance is decreased and thedriving force is lowered. Further, when unnecessary pores are generatedirregularly due to the dispersion in the production, then the electrodeareas of individual devices are dispersed, and the capacitance is alsodispersed. This results in decreasing yield of the devices. Further, itis necessary that the control voltage is adjusted for every individualdevice when the device is used. A problem occurs in that such a deviceis difficult to be used (difficult to be controlled).

[0010] Further, the adhesive force is weak between the wiring patternand the piezoelectric/electrostrictive layer. Therefore, any exfoliationoccurs in some cases during the machining (for example, cutting andpolishing) and/or during the washing (washing with ultrasonic wave) ofthe piezoelectric/electrostrictive device. In the case of the device asdescribed above, the place, at which the exfoliation occurs, is theinterface between the wiring pattern and thepiezoelectric/electrostrictive layer.

[0011] Further, a portion, in which the electrode layer is not formed onthe ceramic substrate, is provided in relation to the planar shape ofthe wiring pattern. At this portion, the ceramic substrate and thepiezoelectric/electrostrictive layer are opposed to one another.However, any gap appears at the portion after the sintering, for thefollowing reason. That is, it is difficult to join constitutivematerials of the ceramic substrate and constitutive materials of thepiezoelectric/electrostrictive layer.

[0012] If such a gap is formed, a part of thepiezoelectric/electrostrictive layer consequently floats over theelectrode layer. Such a portion exists as a region which is notrestricted by the ceramic substrate. As a result, any movement tends tooccur due to any external force in this structure. Therefore, theexfoliation is apt to take place.

[0013] In view of the above, in order that thepiezoelectric/electrostrictive layer and the wiring pattern are notexfoliated from the ceramic substrate, for example, it is necessary thatthe step of cutting the piezoelectric/electrostrictive device isperformed under a condition in which the load on thepiezoelectric/electrostrictive layer or the like is decreased. That is,the cutting step is restricted by the condition in which the machiningload is small. As a result, the machining time is prolonged, and thethroughput is lowered.

[0014] On the other hand, it is necessary that the washing step is alsoperformed under a condition in which the load on thepiezoelectric/electrostrictive layer or the like is decreased.Therefore, in order to eliminate the dirt, it is necessary to use alonger period of washing time. As a result, the number of steps isincreased.

[0015] When the exfoliation of the piezoelectric/electrostrictive layeror the like occurs, the following harmful influences also appear.

[0016] (1) The function as the piezoelectric/electrostrictive device isdeteriorated.

[0017] (2) When the wiring pattern is exfoliated from thepiezoelectric/electrostrictive layer, the capacitance is decreased. As aresult, the amount of generation of strain is decreased in thepiezoelectric/electrostrictive layer, and the displacement is decreased.

[0018] (3) When the wiring pattern is exfoliated from the ceramicsubstrate, then the strain, which is generated in thepiezoelectric/electrostrictive layer, is hardly transmitted to theceramic substrate, and the displacement is decreased.

[0019] (4) The strength of the entire piezoelectric/electrostrictivedevice is decreased, and the resonance frequency is lowered when thepiezoelectric/electrostrictive device is used as an actuator element.

SUMMARY OF THE INVENTION

[0020] The present invention has been made taking the foregoing problemsinto consideration, an object of which is to provide apiezoelectric/electrostrictive device which makes it possible toincrease the occupied area of a conductive portion in one electrodelayer, which increases the driving force, which improves the yield, andwhich is easily controllable, and a method for producing the same.

[0021] Another object of the present invention is to provide apiezoelectric/electrostrictive device which makes it possible toeffectively reduce the volume of a piezoelectric/electrostrictiveelement itself to decrease the resistance on the displacement action andwhich makes it possible to further increase the driving force (increasethe displacement amount) in addition to the requirements describedabove, and a method for producing the same.

[0022] Still another object of the present invention is to provide apiezoelectric/electrostrictive device which makes it possible to preventa piezoelectric/electrostrictive element formed on a ceramic substratefrom exfoliation, reduce the number of steps in relation to theproduction of the piezoelectric/electrostrictive device, and improve thethroughput and which also makes it possible to avoid the deteriorationof function of the piezoelectric/electrostrictive device, and a methodfor producing the same.

[0023] Still another object of the present invention is to provide apiezoelectric/electrostrictive device which makes it possible to improvethe shock resistance by increasing the breaking strength or fracturestrength and which has high reliability, and a method for producing thesame.

[0024] According to the present invention, there is provided apiezoelectric/electrostrictive device comprising a ceramic substrate andat least a piezoelectric/electrostrictive element stacked on the ceramicsubstrate; wherein the piezoelectric/electrostrictive element includes aplurality of piezoelectric/electrostrictive layers and a plurality ofelectrode layers stacked alternately in a comb like structure on theceramic substrate, the electrode layer includes one or more intermediateelectrode layers at an intermediate portion of thepiezoelectric/electrostrictive element, the intermediate electrodelayers are formed by sintering a cermet film containing a conductivematerial and a piezoelectric/electrostrictive material, and in at leastone of the intermediate electrode layers, the conductive materialshrinks in the sintering and forms a conductive portion occupying 80% ormore of the intermediate electrode layer.

[0025] The area described above is herein defined as follows. That is,the maximum straight line lengths of the openings of the individualpores and the number (n) of the pores are measured within a range of asquare having an area of 100 μm² on the electrode surface at amagnification of ×200 by using a metallographic microscope. Assumingthat the shapes of the pores are circular, the pore area is calculatedon condition that an average value (r) of the maximum straight linelengths of the openings is an average diameter. The calculated value ismultiplied by the number (n) of the pores to obtain a multiplied valuefrom which a pore area ratio (h) per 1 mm² is calculated. The expressionof calculation is shown below.

h=nπ(r/2)²×100/1 mm²

[0026] Usually, if the electrode layer is sintered singly or togetherwith the piezoelectric/electrostrictive layer to secure the electrodelayer to the piezoelectric/electrostrictive layer, then a large numberof pores are generated, and/or pores having large opening areas aregenerated, for example, due to the partial evaporation and/or thethermal shrinkage of the electrode layer during the sintering. It isfeared that the portion (conductive portion), which actually functionsas the electrode layer, may be decreased. It is noted that the poresgenerated as described above are filled with thepiezoelectric/electrostrictive material.

[0027] However, in the present invention, the intermediate electrodelayer, which is disposed at the intermediate portion in thepiezoelectric/electrostrictive element, is formed by sintering thecermet film containing the conductive material and thepiezoelectric/electrostrictive material, and the area after thesintering of the conductive portion of one of the intermediate electrodelayers disposed at the intermediate portion inpiezoelectric/electrostrictive element occupies 80% or more of theintermediate electrode layer. Therefore, the unnecessary pores asdescribed above are generated to a smaller extent.

[0028] Therefore, it is possible to increase the occupied area of theconductive portion of one electrode layer. Accordingly, the capacitanceis increased, and the driving force is increased, and thus thedisplacement amount is increased as well.

[0029] The unnecessary pores are scarcely generated in the presentinvention as compared with a case in which the unnecessary pores areirregularly generated. Therefore, the dispersion of the area of theconductive portion of one electrode layer in the individual device isalso decreased. Accordingly, the dispersion of capacitances among theindividual devices is decreased. It is unnecessary that the controlvoltage is adjusted for every device one by one when the device is used.Thus, the device is conveniently usable (easily controllable).

[0030] Similarly, the dispersion of displacement characteristics of theindividual devices is also decreased. Thus, it is possible to improvethe accuracy in relation to the displacement amount.

[0031] The electrode layer included in the electrode layers forconstituting the piezoelectric/electrostrictive element, which isdisposed at the intermediate portion in the stacking direction, isformed by sintering the cermet film containing the conductive materialand the piezoelectric/electrostrictive material. Therefore, a state isgiven, in which the electrode layer and thepiezoelectric/electrostrictive layer are hardly exfoliated fromeach-other.

[0032] Therefore, in the present invention, it is possible to avoid theexfoliation of the piezoelectric/electrostrictive element formed on theceramic substrate, it is possible to reduce the number of steps inrelation to the production of the piezoelectric/electrostrictive device,and it is possible to improve the throughput. Additionally, it ispossible to avoid the deterioration of the function as thepiezoelectric/electrostrictive device as well.

[0033] It is preferable that a range of a volume ratio between theconductive material and the piezoelectric/electrostrictive material is4:6 to 9:1. Further, it is preferable that the intermediate electrodelayer is formed as a conductor layer which is a film of 4 μm or less inthickness. The volume ratio herein refers to the value which iscalculated from masses and specific gravities or densities (providedthat pores are excluded from values) of materials when the materials areblended.

[0034] In this arrangement, it is possible to thin the thickness of oneelectrode layer. Therefore, it is possible to effectively decrease thevolume of the piezoelectric/electrostrictive element itself as well.Accordingly, it is possible to decrease the resistance on thedisplacement action, and it is possible to further increase the drivingforce (increase the displacement amount) in cooperation with theincrease in capacitance.

[0035] It is preferable that the intermediate electrode layer is formedas a cermet conductor layer which is a film of 4 μm or more inthickness. In this arrangement, even when the cermet electrode is 4 μmor more and thick, it is possible to enhance the adhesive force withrespect to the piezoelectric/electrostrictive layer as compared with aconductor layer made of a metal simple substance having the samethickness. Therefore, the exfoliation scarcely occurs, and thisarrangement is advantageous to improve the reliability.

[0036] When the electrode layer, which is disposed at the intermediateportion in the stacking direction, is formed by sintering the cermetfilm containing the conductive material and thepiezoelectric/electrostrictive material, the metal electrode layer isformed at a portion interposed between thepiezoelectric/electrostrictive layers after the sintering. That is, thethin electrode layer based on metal is formed at the portion interposedbetween the piezoelectric/electrostrictive layers, because thepiezoelectric/electrostrictive material component in the cermet film ismoved to the piezoelectric/electrostrictive layer during the sintering,and the remaining metal material forms the electrode layer. In otherwords, the metal electrode layer is formed to be thinner than the cermetelectrode layer. The electrode layer of the present invention is thin,it has a small number of pores, and it has the high adhesive force withrespect to the piezoelectric/electrostrictive layer, as compared with acase in which the electrode layer is formed of a metal paste.

[0037] Further, it is preferable that one or more gaps of one or morelower electrode layers positioned at a lower portion of thepiezoelectric/electrostrictive element is formed on the ceramicsubstrate and the gaps are filled with an insulating layer. In thisarrangement, the insulating layer and the piezoelectric/electrostrictivelayer formed as the upper layer of the insulating layer are stronglybonded. Accordingly, a state is given, in which the electrode layer andthe insulating layer are hardly exfoliated from each other. Therefore,it is possible to avoid the exfoliation of thepiezoelectric/electrostrictive layer formed on the electrode layer, andit is possible to sufficiently exhibit the function of the actuatorelement or the sensor element based on the use of thepiezoelectric/electrostrictive layer.

[0038] It is also preferable that one or more electrode layers providedat an upper portion of the piezoelectric/electrostrictive element, areformed by depositing a film of resinate of a conductive material to theupper portion.

[0039] According to another aspect of the present invention, there isprovided a piezoelectric/electrostrictive device comprising a ceramicsubstrate and a piezoelectric/electrostrictive element formed on theceramic substrate; wherein the ceramic substrate includes fixed sectionswhich have a large thickness and a pair of thin plate sections which areformed continuously from the fixed sections and each of which have athickness thinner than that of the fixed sections; and each of the pairof thin plate sections are composed of two or more types of materials.

[0040] Accordingly, it is possible to increase the breaking strength orfracture strength of the pair of thin plate sections, and it is possibleto improve the shock resistance. This results in the improvement inreliability of the piezoelectric/electrostrictive device.

[0041] It is also preferable to provide a piezoelectric/electrostrictivedevice comprising a ceramic substrate and apiezoelectric/electrostrictive element formed on the ceramic substrate;wherein the ceramic substrate includes fixed sections which have a largethickness and a pair of thin plate sections which are formedcontinuously from the fixed sections and which are thinner than thefixed section; and a second material is used between the pair of thinplate sections and the fixed sections.

[0042] Accordingly, the breaking strength is increased by the secondmaterial between the pair of thin plate sections and the fixed section.Thus, it is possible to improve the shock resistance of the entirepiezoelectric/electrostrictive device.

[0043] When the ceramic substrate has a fixed section which has a largethickness, a pair of thin plate sections which are formed continuouslyfrom the fixed sections and which are thinner than the fixed sections,and movable sections which are provided at ends of the pair of thinplate sections, it is also preferable that a second material is usedbetween at least the pair of thin plate sections and the fixed sectionand between the pair of thin plate sections and the movable sections.

[0044] Accordingly, the breaking strength is increased by the secondmaterial used between the pair of thin plate sections and the fixedsections and between the pair of thin plate sections and the movablesections. Thus, it is possible to improve the shock resistance of theentire piezoelectric/electrostrictive device.

[0045] In this arrangement, it is also preferable that the secondmaterial is used over ranges from between the pair of thin platesections and the fixed sections to between the pair of thin platesections and the movable sections. Accordingly, it is also possible toenhance the strength of portions of the pair of thin plate sectionsother than the joined portions.

[0046] It is also preferable that the second material is a metal. Theceramics have a high breaking strength against the compressive stress,but the breaking strength of the ceramics is low against the tensilestress. On the other hand, the metal has the high breaking strengthagainst the tensile stress, but the breaking strength of the metal islow against the compressive stress. Therefore, when the two materials(ceramics and metal) are combined, it is possible to mutually supplementthe drawbacks of both, and it is possible to secure high strength.

[0047] Further, when the metal is arranged on the surface, the metalcauses elastic deformation in response to the tensile stress, and themetal absorbs the stress. Therefore, the fracture limitation is raised,and the breaking strength is increased as compared with a case in whichthe ceramics is exposed to the surface. In particular, it is possible toenhance the shock resistance.

[0048] It is also preferable that the second material is a cermet. It ispreferable that the metal having a high elastic modulus is directlyarranged on the ceramics. However, there is such a possibility that themetal may be exfoliated. Therefore, it is appropriate to use the cermetwhich has a high joining strength with respect to the ceramics.

[0049] It is preferable that the second material is a cermet composed ofa constitutive material of the ceramic substrate and a metal. In thisarrangement, when the ratio of the metal in the cermet is low, then thejoining strength with respect to the ceramics is increased, but theproperty as the metal becomes poor. Therefore, it is preferable toselect a condition in which the ratio of the metal is high and it ispossible to secure the joining strength with respect to the ceramics.

[0050] It is also preferable that the piezoelectric/ electrostrictiveelement is arranged on at least one thin plate section of the pair ofthin plate sections.

[0051] According to still another aspect of the present invention, thereis provided a method for producing a piezoelectric/electrostrictivedevice comprising a ceramic substrate and apiezoelectric/electrostrictive element formed on the ceramic substrate;the method including a step for manufacturing the ceramic substrate bysintering a molding after forming the molding by using raw materialscontaining a ceramic material; a step for forming thepiezoelectric/electrostrictive element by a plurality ofpiezoelectric/electrostrictive layers and a plurality of electrodelayers stacking alternately in a comb like structure on the ceramicsubstrate; wherein the step for forming thepiezoelectric/electrostrictive element includes a step for forming oneor more intermediate electrode layers at an intermediate portion of thepiezoelectric/electrostrictive element by sintering a cermet filmcontaining a conductive material and a piezoelectric/electrostrictivematerial to form the intermediate electrode layers.

[0052] Accordingly, it is possible to increase the driving force, it ispossible to improve the yield, and it is possible to obtain thepiezoelectric/electrostrictive device which is easily controllable.Further, it is possible to avoid the exfoliation of thepiezoelectric/electrostrictive element formed on the ceramic substrate,it is possible to reduce the number of steps in relation to theproduction of the piezoelectric/electrostrictive device, and it ispossible to improve the throughput. Additionally, it is possible toavoid the deterioration of the function as thepiezoelectric/electrostrictive device.

[0053] In this procedure, it is also preferable that the step forforming said piezoelectric/electrostrictive element includes a step forfilling one or more gaps of one or more lower electrode layerspositioned at a lower portion of the piezoelectric/electrostrictiveelement with an insulating layer to form the lower electrode layers.

[0054] It is also preferable that after a first cermet to be convertedinto the lower electrode layers and a second cermet to be converted intothe insulating layer are formed on the ceramic substrate by printingrespectively, the first and second cermets formed on the ceramicsubstrate by printing are sintered.

[0055] According to still another aspect of the present invention, thereis provided a method for producing a piezoelectric/electrostrictivedevice comprising a ceramic substrate including fixed sections whichhave a large thickness and a pair of thin plate sections which areformed continuously from the fixed sections and which has a thinthickness, and a piezoelectric/electrostrictive element formed on theceramic substrate; the method including a step for forming a cermetpaste by printing on opposing surfaces of a plurality of ceramic greensheets to be converted into the thin plate sections; a step forlaminating the plurality of ceramic green sheets to form a ceramic greenlaminate; a step for sintering the ceramic green laminate to form aceramic laminate; and a step for cutting off unnecessary portions afterforming and sintering the piezoelectric/electrostrictive element on theceramic laminate to manufacture the piezoelectric/electrostrictivedevice in which a second material is used between the pair of thin platesections and the fixed sections.

[0056] Accordingly, it is possible to produce thepiezoelectric/electrostrictive device which makes it possible toincrease the breaking strength of the pair of thin plate sections andwhich makes it possible to improve the shock resistance. Thus, it ispossible to realize the high reliability of thepiezoelectric/electrostrictive device.

[0057] The above and other objects, features, and advantages of thepresent invention will become more apparent from the followingdescription when taken in conjunction with the accompanying drawings inwhich a preferred embodiment of the present invention is shown by way ofillustrative example.

BRIEF DESCRIPTION OF THE DRAWINGS

[0058]FIG. 1 is a perspective view illustrating an arrangement of apiezoelectric/electrostrictive device according to an embodiment of thepresent invention;

[0059]FIG. 2 is a magnified view illustrating apiezoelectric/electrostrictive element of thepiezoelectric/electrostrictive device according to the embodiment of thepresent invention;

[0060]FIG. 3A is a view illustrating a state of a second wiring patternafter sintering the second wiring pattern formed by a metal film;

[0061]FIG. 3B is a view illustrating a state of a second wiring patternafter sintering the second wiring pattern formed by a cermet film;

[0062]FIG. 4 is a view illustrating the process for laminating necessaryceramic green sheets;

[0063]FIG. 5 is a view illustrating a ceramic green laminate laminatedthe ceramic green sheets;

[0064]FIG. 6 is a view illustrating a ceramic laminate formed bysintering the ceramic green laminate and on whichpiezoelectric/electrostrictive elements are formed;

[0065]FIG. 7A is a view illustrating a stage at which a first cermetlayer to be converted into a first layer of a first wiring pattern and asecond cermet layer to be converted into an insulating layer are formedon a ceramic substrate;

[0066]FIG. 7B is a view illustrating a stage at which the first layerand the insulating layer are simultaneously formed on the ceramicsubstrate;

[0067]FIG. 7C is a view illustrating a stage at which a Pt paste to beconverted into a second layer of the first wiring pattern is formed onthe first layer of the first wiring pattern;

[0068]FIG. 8A is a view illustrating a stage at which the second layeris formed on the first layer of the first wiring pattern;

[0069]FIG. 8B is a view illustrating a stage at which a layer to beconverted into a third layer of the first wiring pattern, a PZT paste tobe converted into a first layer piezoelectric/electrostrictive layer,and a fourth cermet layer to be converted into a second wiring patternare formed;

[0070]FIG. 8C is a view illustrating a stage at which the third layer,the first layer piezoelectric/electrostrictive layer, and the secondwiring pattern are simultaneously formed;

[0071]FIG. 9A is a view illustrating a stage at which a PZT paste to beconverted into a second layer piezoelectric/electrostrictive layer and afifth cermet layer to be converted into a third wiring pattern areformed;

[0072]FIG. 9B is a view illustrating a stage at which the second layerpiezoelectric/electrostrictive layer and the third wiring pattern aresimultaneously formed;

[0073]FIG. 9C is a view illustrating a stage at which a PZT paste to beconverted into a third layer piezoelectric/electrostrictive layer and asixth cermet layer to be converted into a fourth wiring pattern areformed;

[0074]FIG. 10A is a view illustrating a stage at which the third layerpiezoelectric/electrostrictive layer and the fourth wiring pattern aresimultaneously formed;

[0075]FIG. 10B is a view illustrating a stage at which a PZT paste to beconverted into fourth layer piezoelectric/electrostrictive layer isformed;

[0076]FIG. 11A is a view illustrating a stage at which the fourth layerpiezoelectric/electrostrictive layer is formed;

[0077]FIG. 11B is a view illustrating a stage at which a Pt resinate tobe converted into a fifth wiring pattern and Au pastes to be convertedinto terminals are formed;

[0078]FIG. 12A is a view illustrating another embodiment correspondingto the production process for the piezoelectric/electrostrictive deviceaccording to the present invention shown in FIGS. 7A;

[0079]FIG. 12B is a view illustrating another embodiment correspondingto the production process for the piezoelectric/electrostrictive deviceaccording to the present invention shown in FIGS. 7B;

[0080]FIG. 12C is a view illustrating another embodiment correspondingto the production process for the piezoelectric/electrostrictive deviceaccording to the present invention shown in FIGS. 7C;

[0081]FIG. 13 is a view illustrating an embodiment in which aninsulating layer composed of a thin film is interposed between a firstportion and a second portion of the first wiring pattern of thepiezoelectric/electrostrictive device according to the embodiment of thepresent invention;

[0082]FIG. 14 is a magnified view illustrating the portion of thepiezoelectric/electrostrictive device according to the embodiment of thepresent invention on which the piezoelectric/electrostrictive element isformed, depicting that the gap is present between the electrode layers;

[0083]FIG. 15 is a front view illustrating apiezoelectric/electrostrictive device according to a modifiedembodiment;

[0084]FIG. 16 is a front view illustrating apiezoelectric/electrostrictive device according to a first specifiedembodiment;

[0085]FIG. 17 is a front view illustrating apiezoelectric/electrostrictive device according to a second specifiedembodiment;

[0086]FIG. 18 is a front view illustrating apiezoelectric/electrostrictive device according to a third specifiedembodiment;

[0087]FIG. 19 is a front view illustrating apiezoelectric/electrostrictive device according to a fourth specifiedembodiment;

[0088]FIG. 20 is a front view illustrating apiezoelectric/electrostrictive device according to a fifth specifiedembodiment;

[0089]FIG. 21 is a front view illustrating apiezoelectric/electrostrictive device according to a sixth specifiedembodiment;

[0090]FIG. 22 is a front view illustrating apiezoelectric/electrostrictive device according to a seventh specifiedembodiment;

[0091]FIG. 23 is a front view illustrating apiezoelectric/electrostrictive device according to an eighth specifiedembodiment; and

[0092]FIG. 24 is a front view illustrating apiezoelectric/electrostrictive device according to a ninth specifiedembodiment.

DETAILED DESCRIPTION OF THE INVENTION

[0093] Embodiments of the piezoelectric/electrostrictive deviceaccording to the present invention and the method for producing the samewill be described below with reference to FIGS. 1 to 24.

[0094] A piezoelectric/electrostrictive device 10 according to thepresent embodiment is a device or element which includes a concept thatthe electric energy and the mechanical energy are mutually convertiblethrough a piezoelectric/electrostrictive element. Therefore, thepiezoelectric/electrostrictive device 10 is preferably an active elementsuch as a variety of actuators and vibrators, and is more preferably adisplacement element for displacing on the basis of the inversepiezoelectric effect and the electrostrictive effect. Thepiezoelectric/electrostrictive device 10 is also preferably a passiveelement such as an acceleration sensor element and a shock sensorelement.

[0095] As shown in FIG. 1, the piezoelectric/electrostrictive device 10according to the present embodiment comprises a ceramic substrate 16which is formed with a pair of thin plate sections 12a, 12b which areopposite, and a fixed section 14 for supporting the thin plate sections12a, 12b. The piezoelectric/electrostrictive device 10 includespiezoelectric/electrostrictive elements 18a, 18b which are formed onrespective parts of the pair of thin plate sections 12a, 12brespectively.

[0096] That is, the piezoelectric/electrostrictive device 10 has afunction such that the pair of thin plate sections 12 a, 12 b aredisplaced by driving the piezoelectric/electrostrictive elements 18 a,18 b, or a function such that the displacement of the thin platesections 12 a, 12 b is detected by the piezoelectric/electrostrictiveelements 18 a, 18 b. Therefore, as shown in FIG. 1, actuator sections 19a, 19 b are constructed by the thin plate sections 12 a, 12 b and thepiezoelectric/electrostrictive elements 18 a, 18 b. Accordingly, thepair of thin plate sections 12 a, 12 b function as vibrating sectionswhich can be vibrated while being supported by the fixed section 14.

[0097] Further, respective forward end portions of the pair of thinplate sections 12 a, 12 b are thick-walled portions which are thickerthan other portions of the pair of thin plate sections 12 a, 12 b, andwhich are formed inwardly a gap (air) 36. The thick-walled portionsfunction as movable sections which are displaceable in accordance withdisplacing the thin plate sections 12 a, 12 b. The thick-walled portionsalso function as attachment sections which hold an object that isinterposed between the end portion of the pair of the thin platesections 12 a, 12 b. The end portions of the pair of thin plate sections12 a, 12 b are hereinafter referred to as “movable sections 20 a, 20 b”.

[0098] The gap (air) 36 may be interposed between opposing end surfaces34 a, 34 b of the movable sections 20 a, 20 b. A plurality of members(not shown) made of the same material as the constitutive material ofthe movable sections 20 a, 20 b or different materials from theconstitutive material of the movable sections 20 a, 20 b may beinterposed between the end surfaces 34 a, 34 b. In this arrangement, theopposing end surfaces 34 a, 34 b of the movable sections 20 a, 20 b alsofunction as attachment surfaces 34 a, 34 b.

[0099] The ceramic substrate 16 is composed of a ceramic stack orlaminate obtained, for example, by integrating a ceramic green stack orlaminate into one unit by the sintering. This feature will be describedlater on.

[0100] The integrated ceramics as described above scarcely suffers fromany secular change of the state, because no adhesive exists on joinedportions of the respective parts. Therefore, the joined portions arehighly reliable, and the structure is advantageous to secure therigidity. Further, such an integrated ceramics can be produced with easein accordance with the ceramic green sheet-laminating method asdescribed later on.

[0101] After the ceramic substrate 16 and thepiezoelectric/electrostrictive elements 18 a, 18 b are preparedseparately as described later on, the piezoelectric/electrostrictiveelements 18 a, 18 b are directly formed on the ceramic substrate 16 byusing the film formation method for the ceramic substrate 16.

[0102] Each of the piezoelectric/electrostrictive elements 18 a, 18 bcomprises a piezoelectric/electrostrictive layer 22 and a pair ofelectrodes 24, 26 formed on both sides of thepiezoelectric/electrostrictive layer 22. The first electrode 26 of thepair of electrodes 24, 26 is formed at least on each of the pair of thinplate sections 12 a, 12 b.

[0103] In the embodiment of the present invention, the following casewill be principally explained. That is, each of thepiezoelectric/electrostrictive layer 22 and the pair of electrodes 24,26 has a multilayered structure. The first electrode 24 and the secondelectrode 26 are alternately stacked respectively so that cross sectionsof the electrodes 24, 26 are comb-shaped cross sections. The firstelectrode 24 and the second electrode 26 are overlapped with each otherwith the piezoelectric/electrostrictive layer 22 interveningtherebetween. As a result, each of the piezoelectric/electrostrictiveelements 18 a, 18 b has a multiple stage structure. However, there is nolimitation to the multilayered structure. A single layer structure maybe used.

[0104] As shown in a magnified view in FIG. 2, each of thepiezoelectric/electrostrictive elements 18 a, 18 b includes thepiezoelectric/electrostrictive layer 22 which has a four-layeredstructure (first to fourth layers of piezoelectric/electrostrictivelayers 22A to 22D).

[0105] In particular, a first wiring pattern 50 is formed substantiallyover respective side surfaces of the thin plate section 12 a, 12 b, themovable section 20 a, 20 b, and the fixed section 14 of the ceramicsubstrate 16. The first wiring pattern 50 is separated into a firstportion 24A (portion to constitute the first electrode 24) and a secondportion 26A (portion to constitute the second electrode 26) on the sidesurface of the fixed section 14 by a gap 40.

[0106] The gap 40 is filled with an insulating layer 42 which functionsas an insulating section 44 of the first wiring pattern 50.

[0107] The first electrode 24 is formed in a comb-shaped form which iscomprised of the first portion 24A of the first wiring pattern 50, asecond wiring pattern 24B formed on the upper surface of the first layerpiezoelectric/electrostrictive layer 22A, and a fourth wiring pattern24C formed on the upper surface of the third layerpiezoelectric/electrostrictive layer 22C.

[0108] The second electrode 26 is formed in a comb-shaped form which iscomprised of the second portion 26A of the first wiring pattern 50, athird wiring pattern 26B formed on the second layerpiezoelectric/electrostrictive layer 22B, and a fifth wiring pattern 26Cformed on the upper surface of the fourth layerpiezoelectric/electrostrictive layer 22D.

[0109] A first terminal 28 is formed on the upper surface of a stackstacked by the first portion 24A of the first wiring pattern 50, thesecond wiring pattern 24B, and the fourth wiring pattern 24C. A secondterminal 30 is formed at the end of the fifth wiring pattern 26C whichis located on the uppermost layer.

[0110] The insulating section 44 has, for example, the followingeffects. That is, (1) the actuator is not driven at the backward end 46of the piezoelectric/electrostrictive element 18 a, 18 b (portionranging from the end of the gap 40 on the backward end side to thebackward end of the fixed section 14), and (2) any short circuit isrestrained at the edge of the first terminal 28.

[0111] As shown in FIG. 2, in the piezoelectric/electrostrictive device10 according to this embodiment, the first wiring pattern 50 has athree-layered structure.

[0112] Specifically, the first wiring pattern 50 includes a first layer140 which is formed directly on the ceramic substrate 16 and which iscomposed of a cermet of a substrate material and an electrode material,a second layer 142 which is formed on the first layer 140 and which iscomposed of an electrode material, and a third layer 144 which is formedon the second layer 142 and which is composed of a cermet of apiezoelectric/electrostrictive material and an electrode material.

[0113] Further, in this embodiment, the fifth wiring pattern 26Cdisposed at the uppermost layer of the second electrode 26 is composedof a resinate of an electrode material. Each of the wiring patterns(second to fourth wiring patterns 24B, 26B, 24C) of the respectiveelectrode layers formed in the piezoelectric/electrostrictive element 18a, 18 b is constructed by sintering a cermet film containing anelectrode material and a piezoelectric/electrostrictive material.Further, each of the second to fourth wiring patterns 24B, 26B, 24Cafter the sintering is constituted such that the area of the conductiveportion of each of the wiring patterns 24B, 26B, 24C occupies 80% ormore of the area to be occupied by each of the wiring patterns 24B, 26B,24C.

[0114] For example, it is assumed that the second wiring pattern 24B iscomposed of a metal film, and that the wiring pattern 24B is sinteredonly the piezoelectric/electrostrictive layer 22 or together with thepiezoelectric/electrostrictive layer 22 to secure the wiring pattern 24Bto the piezoelectric/electrostrictive layer 22. On this condition, asshown in FIG. 3A, a lot of unnecessary pores 62 and pores having largeopening areas are generated in the second wiring pattern 24B by anypartial evaporation or any thermal shrinkage of the second wiringpattern 24B during the sintering. As a result, the portion (conductiveportion), which actually functions as the second wiring pattern 24B, isdecreased. The diameters of the unnecessary pores 62 generated asdescribed above are about 3 to 50 μm. Therefore, the unnecessary pores62 are filled with the piezoelectric/electrostrictive material.

[0115] However, in the present embodiment, as shown in FIG. 3B, thesecond wiring pattern 24B is formed by sintering the cermet filmcontaining the conductive material and thepiezoelectric/electrostrictive material. The area of the conductiveportion in the second wiring pattern 24B after the sintering increases80% or more to the area which would be occupied by the second wiringpattern 24B. Therefore, the area of the unnecessary pores 62 asdescribed above is decreased. The aforementioned feature on the secondwiring pattern 24B is also obtained in the third and fourth wiringpatterns 26B, 24C.

[0116] Further, it is preferable that the volume ratio between theelectrode material and the piezoelectric/electrostrictive material is4:6 to 9:1 so that the second to fourth wiring patterns 24B, 26B, 24Cfunction as the conductor layers. If the blending ratio of the electrodematerial of the volume ratio is smaller than 4, the wiring pattern 24B,26B, 24C hardly functions as the conductor. On the other hand, if theblending ratio is larger than 9, both of the effect to thin theelectrode and the adhesive force with respect to thepiezoelectric/electrostrictive layer may be reduced. When the blendingcondition as described above satisfies the volume ratio, each of theintermediate patters can be constructed as the conductor layer being 4μm or less in thickness. Further, the so-called breakage, in which theconductive portion locally disappears, is not caused. Thus, it ispossible to obtain a pattern shape substantially exactly as designed.

[0117] When each of the second to fourth wiring patterns 24B, 26B, 24Cis formed by sintering the cermet film containing the conductivematerial and the piezoelectric/electrostrictive material, the effect onthe second to fourth wiring patterns 24B, 26B, 24C will be described.Firstly, a thin conductor layer is formed by performing the sinteringafter forming the cermet film.

[0118] That is, the piezoelectric/electrostrictive material componentsin the cermet film are moved to the piezoelectric/electrostrictivelayers 22 during the sintering, and the remaining metal material formsthe conductor layer. Therefore, the thin conductor layer, which is basedon the metal, is formed at the portion interposed between thepiezoelectric/electrostrictive layers 22. In this process, the portionwhich is not interposed between the piezoelectric/electrostrictivelayers 22, for example, the portion on which the terminal 28 is formedas shown in FIG. 2 is formed as a cermet electrode layer in which themetal material and the piezoelectric/electrostrictive material are mixedwith each other, i.e., a cermet electrode layer which is thicker thanthe conductor layer. However, even when the thickness of the cermetelectrode layer is 4 μm or more, it is possible to increase the adhesiveforce with respect to the piezoelectric/electrostrictive layer 22 ascompared with an electrode layer composed of a metal simple substancehaving the same thickness. Therefore, the exfoliation is hardly caused,and such a cermet electrode layer is advantageous to improve thereliability.

[0119] As described above, each of the second to fourth wiring patterns24B, 26B, 24C described above is the electrode layer which is thin,includes the unnecessary pores 62 to a smaller extent, and which has thehigh adhesive force with respect to the piezoelectric/electrostrictivelayer 22 as compared with the case in which the electrode layer isformed of a metal paste.

[0120] Next, a method for producing the piezoelectric/electrostrictivedevice 10 according to the present embodiment will be described withreference to FIGS. 4 to 11B. At first, the following terms are defined.A ceramic green laminate 58 is defined as a laminate which is obtainedby laminating ceramic green sheets (see, for example, FIG. 5). A ceramicstack or laminate 60 is defined as a product which is obtained bysintering the ceramic green laminate 58 into one unit (see, for example,FIG. 6). A ceramic substrate 16 is defined as a product which isobtained by cutting off unnecessary portions from the ceramic stack orlaminate 60 to integrally have the thin plate sections 12 a, 12 b andthe fixed section 14 (see FIG. 1).

[0121] In this method, after a plurality ofpiezoelectric/electrostrictive devices 10 are arranged in a verticaldirection and in a lateral direction respectively on an identicalsubstrate, the ceramic laminate 60 is cut off per chip unit so that anumber of piezoelectric/electrostrictive devices 10 are finally obtainedin identical steps. However, in order to simplify the explanation, amethod for producing one piezoelectric/electrostrictive device 10 willbe described.

[0122] At first, a binder, a solvent, a dispersing agent, a plasticizer,and other components are added with a ceramic powder such as zirconiaand these are mixed to prepare a slurry. Next, the slurry is subjectedto a defoaming treatment to thereafter prepare ceramic green sheetshaving a predetermined thickness by the method such as the reverse rollcoater method and the doctor blade method.

[0123] Subsequently, the ceramic green sheets are machined a variety ofshapes as shown in FIG. 4, for example, by the method such as the lasermachining and the punching out based on the use of a die to obtain aplurality of ceramic green sheets 70A to 70D, 72A, 72B, 102A to 102G forforming the substrate.

[0124] The ceramic green sheets 70A to 70D are a plurality of (forexample, two) ceramic green sheets provided with windows 100 for formingthe movable sections 20 a, 20 b having the end surfaces 34 a, 34 b ofthe piezoelectric/electrostrictive device 10. On the other hand, theceramic green sheets 102A to 102G are a plurality of (for example, four)sheets formed with windows 54 for forming the space at least between thethin plate sections 12 a, 12 b. The numbers of ceramic green sheets asdescribed above are an example.

[0125] Subsequently, as shown in FIG. 5, after the ceramic green sheets70A to 70D, 72A, 72B, 102A to 102G are laminated so that the ceramicgreen sheets 70A to 70D, 102A to 102G are interposed between the ceramicgreen sheets 72A, 72B, the ceramic green laminate 58 is formed bysecuring the above-mentioned ceramic green sheet under pressure. Whenthe lamination is performed, the ceramic green sheets are laminatedwhile arranging the ceramic green sheets 102A to 102G at the center.

[0126] During this process, the pressure may not be applied to someportions of the ceramic green laminate 58 during the securing under thepressure, due to the presence of the windows 100. Therefore, it isnecessary to change, for example, the order of the lamination and thesecuring under the pressure so that such portions do not appear. Afterthat, the ceramic green laminate 58 is sintered to obtain the ceramiclaminate 60 (see FIG. 6).

[0127] Subsequently, as shown in FIG. 6, thepiezoelectric/electrostrictive elements 18 a, 18 b as the multilayeredstructure, are formed on the both surfaces of the ceramic laminate 60,i.e., on the surfaces laminated the ceramic green sheets 72A, 72B of theceramic laminate 60. The piezoelectric/electrostrictive elements 18 a,18 b and the ceramic laminate 60 are integrated into one unit by thesintering. Of course, the piezoelectric/electrostrictive element may beformed on only the surface on one side.

[0128] The process for forming the piezoelectric/electrostrictiveelement 18 a having the multilayered structure on one surface of theceramic laminate 60 will be described in detail with reference to FIGS.7A to 11B. The process for forming the piezoelectric/electrostrictiveelement 18 b is equivalent to the process for forming thepiezoelectric/electrostrictive element 18 a, any duplicate explanationof which will be herein omitted.

[0129] At first, as shown in FIG. 7A, a first cermet layer 160, which iscomposed of, for example, Pt/zirconia, is formed on one surface of theceramic laminate 60, for example, by the screen printing. After that, asecond cermet layer 162, which is composed of, for example, Pt/zirconia,is formed on the portion (portion corresponding to the gap 40 shown inFIG. 2) at which the first cermet layer 160 is separated or divided, forexample, by the screen printing. In this process, the respectivethicknesses of the first cermet layer 160 and the second cermet layer162 are set so that the thicknesses after the sintering are about 1 μmand about 5 μm respectively.

[0130] After that, as shown in FIG. 7B, the first layer 140 (first layerfor constituting the first wiring pattern 50) based on the first cermetlayer 160 and the insulating layer 42 based on the second cermet layer162 are formed on the surface of the ceramic laminate 60 by a sinteringtreatment which maintains the first cermet layer 160 and the secondcermet layer 162 at a temperature of 1000 to 1400° C. for about 0.5 to 3hours.

[0131] After that, as shown in FIG. 7C, for example, a Pt paste 164 isformed on the first layer 140, for example, by the screen printing. Inthis process, the thickness of the Pt paste 164 is set so that thethickness after the sintering is 2 to 5 μm.

[0132] After that, as shown in FIG. 8A, the second layer 142 (secondlayer for constituting the first wiring pattern 50) based on the Ptpaste 164 is formed on the first layer 140 by a sintering treatmentwhich maintains the Pt paste 164 at a temperature of 1000 to 1400° C.for about 0.5 to 3 hours.

[0133] After that, as shown in FIG. 8B, a third cermet layer 166, whichis composed of, for example, Pt/PZT, is formed on the second layer 142,for example, by the screen printing. In this process, the thickness ofthe third cermet layer 166 is set so that the thickness after thesintering is 0.5 to 5 μm.

[0134] Subsequently, for example, a first layer PZT paste 168 is formedon the third cermet layer 166 and on the exposed insulating layer 42,for example, by the screen printing. In this process, the thickness ofthe PZT paste 168 is set so that the thickness after the sintering is 5to 25 μm.

[0135] Subsequently, for example, a fourth cermet layer 170 of Pt/PZT,which is to be converted into the second wiring pattern 24B thereafter,is formed on the PZT paste 168 and on a first portion 166a (portioncorresponding to the first portion 24A of the first wiring pattern 50thereafter) of the exposed third cermet layer 166, for example, by thescreen printing. In this process, the thickness of the fourth cermetlayer 170 is set so that the thickness after the sintering is 1 to 3 μm.

[0136] After that, as shown in FIG. 8C, the third layer 144 (third layerfor constituting the first wiring pattern 50) based on the third cermetlayer 166, the first layer piezoelectric/electrostrictive layer 22Abased on the PZT paste 168, and the second wiring pattern 24B based onthe fourth cermet layer 170 are formed by a sintering treatment whichmaintain the third cermet layer 166, the PZT paste 168 and the fourthcermet layer 170 at a temperature of 1000 to 1400° C. for about 0.5 to 3hours.

[0137] In this procedure, the second wiring pattern 24B is composed ofthe fourth cermet layer 170 of Pt/PZT. Therefore, the thermal shrinkageand the partial evaporation are scarcely caused upon the sintering to beperformed thereafter. For example, as shown in FIG. 3B, the generationof unnecessary pores 62 is greatly suppressed. Further, the secondwiring pattern 24B is constituted as the conductor layer having its filmof 4 μm or less in thickness.

[0138] After that, as shown in FIG. 9A, for example, a second layer PZTpaste 172 is formed on the second wiring pattern 24B and on the exposedfirst layer piezoelectric/electrostrictive layer 22A, for example, bythe screen printing. In this process, the thickness of the PZT paste 172is set so that the thickness after the sintering is 5 to 25 μm.

[0139] Subsequently, a fifth cermet layer 174, which is composed of, forexample, Pt/PZT and which is to be converted into the third wiringpattern 26B, is formed on the PZT paste 172 and on the second portion26A of the first wiring pattern 50, for example, by the screen printing.In this process, the thickness of the fifth cermet layer 174 is set sothat the thickness after the sintering is 1 to 3 μm.

[0140] After that, as shown in FIG. 9B, the second layerpiezoelectric/electrostrictive layer 22B based on the PZT paste 172 andthe third wiring pattern 26B based on the fifth cermet layer 174 areformed by a sintering treatment which maintains the PZT paste 172 andthe fifth cermet layer 174 at a temperature of 1000 to 1400° C. forabout 0.5 to 3 hours. Also in this procedure, the third wiring pattern26B is composed of the fifth cermet layer 174 of Pt/PZT. Therefore, thegeneration of unnecessary pores 62 is greatly suppressed even upon thesintering to be performed thereafter. Further, the third wiring pattern26B is constituted as the conductor layer having its film of 4 μm orless in thickness.

[0141] After that, as shown in FIG. 9C, for example, a third layer PZTpaste 176 is formed on the third wiring pattern 26B and the exposedsecond layer piezoelectric/electrostrictive layer 22B, for example, bythe screen printing. In this process, the thickness of the PZT paste 176is set so that the thickness after the sintering is 5 to 25 μm.

[0142] Subsequently, a sixth cermet layer 178, which is composed of, forexample, Pt/PZT and which is to be converted into the fourth wiringpattern 24C, is formed on the PZT paste 176 and on the exposed secondwiring pattern 24B, for example, by the screen printing. In thisprocess, the thickness of the sixth cermet layer 178 is set so that thethickness after the sintering is 1 to 3 μm.

[0143] After that, as shown in FIG. 10A, the third layerpiezoelectric/electrostrictive layer 22C based on the PZT paste 176 andthe fourth wiring pattern 24C based on the sixth cermet layer 178 areformed by a sintering treatment which maintains the PZT paste 176 andthe sixth cermet layer 178 at a temperature of 1000 to 1400° C. forabout 0.5 to 3 hours. Also in this procedure, the fourth wiring pattern24C is composed of the sixth cermet layer 178 of Pt/PZT. Therefore, thegeneration of unnecessary pores 62 is greatly suppressed even upon thesintering to be performed thereafter. Further, the fourth wiring pattern24C is constituted as the conductor layer having its film of 4 μm orless in thickness.

[0144] After that, as shown in FIG. 10B, for example, a fourth layer PZTpaste 180 is formed on the fourth wiring pattern 24C and on the exposedthird layer piezoelectric/electrostrictive layer 22C, for example, bythe screen printing. In this process, the thickness of the PZT paste 180is set so that the thickness after the sintering is 5 to 25 μm.

[0145] After that, as shown in FIG. 11A, the fourth layerpiezoelectric/electrostrictive layer 22D based on the PZT paste 180 isformed on the third layer piezoelectric/electrostrictive layer 22C andthe fourth wiring pattern 24C by a sintering treatment which maintainsthe PZT paste 180 at a temperature of 1000 to 1400° C. for about 0.5 to3 hours.

[0146] After that, as shown in FIG. 11B, for example, a Pt resinate 182,which is to be converted into the fifth wiring pattern 26C thereafter,is formed on the fourth layer piezoelectric/electrostrictive layer 22D,on the exposed third wiring pattern 26B, and on the exposed secondportion 26A of the first wiring pattern 50, for example, by the screenprinting. In this process, the thickness of the Pt resinate 182 is setso that the thickness after the sintering is 0.1 to 3 μm.

[0147] Subsequently, Au pastes 184, 186, which are to be converted intothe first terminal 28 and the second terminal 30 thereafterrespectively, are formed on the exposed first portion 24A of the firstwiring pattern 50 and on the end of the Pt resinate 182, for example, bythe screen printing.

[0148] After that, the fifth wiring pattern 26C based on the Pt resinate182 and the terminals 28, 30 based on the Au pastes 184, 186 are formedby a sintering treatment which maintains the Pt resinate 182 and theterminals 28, 30 at a temperature of 500 to 1000° C. for about 0.5 to 3hours. Accordingly, as shown in FIG. 2, thepiezoelectric/electrostrictive element 18 a having the multilayeredstructure is formed on one surface of the ceramic laminate 60. Thepiezoelectric/electrostrictive element 18 b having the multilayeredstructure is also formed on the other surface of the ceramic laminate 60by the same or equivalent method.

[0149] After that, as shown in FIG. 6, side portions and a forward endportion of the ceramic laminate 60 are cut off by cutting the ceramiclaminate 60 formed with the piezoelectric/electrostrictive elements 18a, 18 b along cutting lines C1, C2, C5. As a result of the cutoff, asshown in FIG. 1, the piezoelectric/electrostrictive device 10, in whichthe piezoelectric/electrostrictive elements 18 a, 18 b are formed on theceramic substrate 16, is obtained, and the movable sections 20 a, 20 bhaving the opposing end surfaces 34 a, 34 b are formed respectively. =pSeveral orders or timings of cutting are applicable. That is, thecutting may be performed along the cutting line C5 after performing thecutting along the cutting lines C1, C2. Alternatively, the cutting maybe performed along the cutting lines C1, C2 after performing the cuttingalong the cutting line C5. Of course, these cutting operations may beperformed simultaneously. The end surface of the fixed section 14opposed to the cutting line C5 may be appropriately cut.

[0150] After that, scraps or the like resulting from the cutting areremoved, for example, by the ultrasonic cleaning.

[0151] As described above, in the piezoelectric/electrostrictive device10 according to the embodiment, the second to fourth wiring patterns24B, 26B, 24C, which are disposed at the intermediate portions in thestacking direction, are formed by sintering the cermet films each ofwhich contains the conductive material and thepiezoelectric/electrostrictive material. Therefore, it is possible toincrease the occupied area occupied by the conductive portion of each ofthe electrode layers. Accordingly, the capacitance is increased, thedriving force is increased, and thus the displacement amount isincreased as well.

[0152] Further, the unnecessary pores 62 are hardly generated in theembodiment of the present invention as compared with the case in whichthe unnecessary pores 62 are irregularly generated. Therefore, thedispersion of the area of the conductive portion of one electrode layerof the individual device is also decreased. Accordingly, the dispersionof capacitances among the individual devices is decreased. It isunnecessary that the control voltage is adjusted for every device one byone when the device is used. Thus, the device is conveniently usable(easily controllable).

[0153] Similarly, the dispersion of displacement characteristics of theindividual devices is also decreased. Thus, it is possible to improvethe accuracy in relation to the displacement amount.

[0154] Further, in the second to fourth wiring patterns 24B, 26B, 24Cdescribed above, the thickness of each of the conductor layers can bethinned to be 4 μm. Therefore, it is possible to effectively decreasethe volume of the piezoelectric/electrostrictive element 18 a, 18 bitself as well. Accordingly, it is possible to decrease the resistanceon the displacement action, and it is possible to further increase thedriving force (increase the displacement amount) in cooperation with theincrease in capacitance.

[0155] Further, the first wiring pattern 50 is strongly bonded to theceramic substrate 16 and the first layer piezoelectric/electrostrictivelayer 22A by the film formation method. Further, owing to the insulatinglayer 42 charged into the gap 40 of the first wiring pattern 50, anypart of the first layer piezoelectric/electrostrictive layer 22A isnever arranged on the gap 40. Accordingly, it is possible to reliablyavoid the exfoliation of the piezoelectric/electrostrictive layer 22Aduring the machining and during the washing.

[0156] As a result, the cutting step for the ceramic laminate 60 is notrestricted by any condition in which the machining load is small.Therefore, the machining time is shortened, and it is possible toimprove the throughput.

[0157] It is also unnecessary that the washing step is performed under acondition in which the load on the piezoelectric/electrostrictive layer22A or the like is decreased. Thus, it is possible to efficientlyshorten the washing time, and it is possible to realize the reduction ofthe number of steps.

[0158] In the embodiment illustrated in FIGS. 7A to 7C described above,the second cermet layer 162, which has the thickness larger than that ofthe first cermet layer, is formed at the portion at which the firstcermet layer 160 is separated, the heat treatment is thereafter appliedso that the first cermet layer 160 is converted into the first layer 140and the second cermet layer 162 is converted into the insulating layer42, and then the Pt paste 164 is formed on the first layer 140.Alternatively, the production may be performed as shown in FIGS. 12A to12C.

[0159] That is, as shown in FIG. 12A, a second cermet layer 162, whichhas substantially the same thickness as the thickness of the firstcermet layer 160 and which has a width larger than the width of theportion at which the first cermet layer 160 is separated, is formed atthe portion at which the first cermet layer 160 is separated.

[0160] After that, as shown in FIG. 12B, the first layer 140 based onthe first cermet layer 160 and form an insulating layer 42 based on thesecond cermet layer 162 is formed by a sintering treatment whichmaintains the first cermet layer 160 and the second cermet layer 162 ata temperature of 1000 to 1400° C. for about 0.5 to 3 hours.

[0161] After that, as shown in FIG. 12C, for example, a Pt paste 164 isformed on the first layer 140, for example, by the screen printing. Inthis process, the Pt paste 164 is formed so that the shoulders of theinsulating layer 42 are coated with the Pt paste 164 and the centralportion of the insulating layer 42 is exposed.

[0162] After that, the same steps as the steps shown in FIGS. 8A to 11Bare executed, and thus a form is obtained as shown in FIG. 13, in whichthe insulating layer 42 is interposed between the first portion 24A andthe second portion 26A of the first wiring pattern 50. Therefore, it ispossible to reliably avoid the exfoliation of thepiezoelectric/electrostrictive layer 22A during the machining and duringthe washing.

[0163] In particular, the insulating layer 42 shown in FIG. 13 is a thinfilm unlike the insulating layer 42 shown in FIG. 2. Therefore, thepiezoelectric/electrostrictive layer 22A, which is formed as the upperlayer, enters the space between the first portion 24A and the secondportion 26A of the first wiring pattern 50, and the adhesion performanceof the piezoelectric/electrostrictive layer 22A is improved owing to theso-called anchor effect.

[0164] Further, in this form, both sides of the insulating layer 42 arefirmly held by the second layer 142 and the third layer 144. Therefore,these components function similarly to the so-called eyelet. It ispossible to improve the adhesion performance of the insulating layer 42and the first wiring pattern 50 with respect to the ceramic laminate 60.

[0165] Further, this production method can be carried out whilemitigating the accuracy of the mask alignment or adjustment as comparedwith the production method shown in FIGS. 7A to 7C. Therefore, it ispossible effectively simplify the production steps, and it is possibleto effectively reduce the number of steps.

[0166] As shown in FIG. 14, it is also allowable that the gap 40 may beprovided as it is without changing the insulating layer 42 in the stepsdescribed above.

[0167] Next, the respective constitutive elements of thepiezoelectric/electrostrictive device 10 according to the presentembodiment will be explained.

[0168] The movable sections 20 a, 20 b are the parts which are operatedon the basis of the driving amounts of the thin plate sections 12 a, 12b as described above. A variety of members are attached theretodepending on the purpose of use of the piezoelectric/electrostrictivedevice 10. For example, when the piezoelectric/electrostrictive device10 is used as a displacement element, a shield plate for an opticalshutter or the like is attached. In particular, when thepiezoelectric/electrostrictive device 10 is used for the positioning ofa magnetic head of a hard disk drive or for a ringing-suppressingmechanism, a member required to be positioned, including, for example, amagnetic head, a slider provided with a magnetic head, and a suspensionprovided with a slider is attached.

[0169] The fixed section 14 is the part which supports the thin platesections 12 a, 12 b and the movable sections 20 a, 20 b as describedabove. For example, when the piezoelectric/electrostrictive device 10 isutilized to position a magnetic head of a hard disk drive as describedabove, the fixed section 14 is supported by and secured to, for example,a carriage arm attached to VCM (voice coil motor) or a suspension or afixed plate attached to the carriage arm. Accordingly, the entirepiezoelectric/electrostrictive device 10 is fixed. Further, as shown inFIG. 1, the terminals 28, 30 and other members for driving thepiezoelectric/electrostrictive elements 18 a, 18 b are arranged on thefixed section 14 in some cases.

[0170] The materials for constituting the movable sections 20 a, 20 band the fixed section 14 are not specifically limited as long as thematerials have certain rigidity. However, the ceramics, to which theceramic green sheet-laminating method is applicable as described above,can be preferably used.

[0171] Specifically, there may be exemplified materials containing amajor component of zirconia represented by fully stabilized zirconia andpartially stabilized zirconia, alumina, magnesia, silicon nitride,aluminum nitride, and titanium oxide. Further, there may be exemplifiedmaterials containing a major component of a mixture thereof. However, itis preferable to use a material containing a major component ofzirconia, especially fully stabilized zirconia and a material containinga major component of partially stabilized zirconia, in view of the highmechanical strength and the high toughness.

[0172] The thin plate sections 12 a, 12 b are the parts which are drivenin accordance with the displacement of thepiezoelectric/electrostrictive elements 18 a, 18 b as described above.Each of the thin plate sections 12 a, 12 b is a thin plate-shaped memberhaving flexibility. The thin plate sections 12 a, 12 b function toamplify the expansion and contracting displacement of thepiezoelectric/electrostrictive element 18 a, 18 b arranged on thesurface to obtain the bending displacement which is transmitted to themovable sections 20 a, 20 b. Therefore, as for the shape and thematerial quality of the thin plate section 12 a, 12 b, it is enough touse those having flexibility and having mechanical strength to such anextent that no breakage occurs due to any bending deformation. The shapeand the material quality of the thin plate sections 12 a, 12 b can beappropriately selected in consideration of the response performance andthe operability of the thin plate sections 12 a, 12 b.

[0173] Ceramics can be preferably used for the material for constitutingthe thin plate sections 12 a, 12 b, in the same manner as for themovable sections 20 a, 20 b and the fixed section 14. A materialcontaining a major component of zirconia, especially fully stabilizedzirconia, and a material containing a major component of partiallystabilized zirconia are used most preferably, because the mechanicalstrength is large even when the wall thickness is thin, the toughness ishigh, and the reactivity with the piezoelectric/ electrostrictive layer22 and the electrode material is small.

[0174] The fully stabilized zirconia and the partially stabilizedzirconia are preferably fully stabilized or partially stabilized asfollows. That is, compounds which fully stabilize and/or partiallystabilize zirconia include yttrium oxide, ytterbium oxide, cerium oxide,calcium oxide, and magnesium oxide. Zirconia can be stabilized asdesired, by adding and containing at least one of the foregoingcompounds, or by adding the foregoing compounds in combination as well,while there is no limitation to only the addition of one compound.

[0175] It is desirable that the respective compounds are added in thefollowing amounts, i.e., 1 to 30 mole %, preferably 1.5 to 10 mole % inthe case of yttrium oxide or ytterbium oxide, 6 to 50 mole %, preferably8 to 20 mole % in the case of cerium oxide, and 5 to 40 mole %,preferably 5 to 20 mole % in the case of calcium oxide or magnesiumoxide. Among them, it is especially preferable to use yttrium oxide as astabilizer. In this case, it is desirable that yttrium oxide ispreferably added in an amount of 1.5 to 10 mole %, and more preferably 2to 4 mole %. It is possible to add, for example, alumina, silica, and/oroxide of transition metal as an additive of a sintering aid or the likewithin a range of 0.05 to 20% by weight. However, when a technique forforming the piezoelectric/electrostrictive elements 18 a, 18 b isadopted, i.e., when the piezoelectric/electrostrictive elements 18 a, 18b are formed by sintering and integrating materials into one unit by thefilm formation method, then it is also preferable to add, for example,alumina, magnesia, and/or oxide of transition metal as an additive.

[0176] In order to obtain high mechanical strength and stable crystalphase, it is desirable that the average crystal grain diameter ofzirconia is 0.05 to 3 μm, preferably 0.05 to 1 μm. As described above,ceramics, which are equivalent to those used for the movable sections 20a, 20 b and the fixed section 14, can be used for the thin platesections 12 a, 12 b. However, the thin plate sections 12 a, 12 b arepreferably constructed by using substantially the same material, whichis advantageous in order that the reliability of the joined portions isimproved, the strength of the piezoelectric/electrostrictive device 10is enhanced, and the complexity of production is reduced.

[0177] Each of the piezoelectric/electrostrictive elements 18 a, 18 bhas at least the piezoelectric/electrostrictive layer 22 and the pair ofelectrodes 24, 26 for applying the electric field to thepiezoelectric/electrostrictive layer 22. It is possible to use, forexample, piezoelectric/electrostrictive elements of the unimorph typeand the bimorph type. However, the piezoelectric/electrostrictiveelement of the unimorph type, which is combined with the thin platesection 12 a, 12 b, is more excellent in stability of the generateddisplacement amount, and it is more advantageous to reduce the weight.Therefore, the piezoelectric/electrostrictive element of the unimorphtype is suitable for the piezoelectric/electrostrictive device 10 asdescribed above.

[0178] It is preferable that the piezoelectric/electrostrictive elements18 a, 18 b are formed on the side surfaces of the thin plate sections 12a, 12 b as shown in FIG. 1, since the thin plate sections 12 a, 12 b canbe driven more greatly.

[0179] Piezoelectric ceramics are preferably used for thepiezoelectric/electrostrictive layer 22. However, it is also possible touse electrostrictive ceramics, ferroelectric ceramics, andanti-ferroelectric ceramics. However, when thepiezoelectric/electrostrictive device 10 is used to position themagnetic head of the hard disk drive, for example, it is preferable touse a material having small strain hysteresis, and it is preferable touse a material having a coercive electric field of 10 kV/mm or less,because the linearity between the displacement amount of the thin platesection 12 a, 12 b and the driving voltage or the output voltage isconsidered to be important.

[0180] Specified materials include ceramics containing, for example,lead zirconate, lead titanate, lead magnesium niobate, lead nickelniobate, lead zinc niobate, lead manganese niobate, lead antimonystannate, lead manganese tungstate, lead cobalt niobate, bariumtitanate, sodium bismuth titanate, potassium sodium niobate, and/orstrontium bismuth tantalite singly or as a mixture.

[0181] In particular, a material containing lead zirconate, leadtitanate, or lead magnesium niobate as a major component, or a materialcontaining sodium bismuth titanate as a major component is preferablyused, since such a material has a high electromechanical coupling factorand a high piezoelectric constant, the reactivity with the thin platesection (ceramics) 12 a, 12 b is small when thepiezoelectric/electrostrictive layer 22 is sintered, and a stablecomposition is obtained.

[0182] It is also preferable to use ceramics obtained by adding, to thematerial described above, any single one of or a mixture of, forexample, oxides of lanthanum, calcium, strontium, molybdenum, tungsten,barium, niobium, zinc, nickel, manganese, cerium, cadmium, chromium,cobalt, antimony, iron, yttrium, tantalum, lithium, bismuth, andstannum.

[0183] For example, when lanthanum and/or strontium is contained inmajor components of lead zirconate, lead titanate, and lead magnesiumniobate, an advantage is obtained in some cases, for example, such thatthe coercive electric field and the piezoelectric characteristics areadjustable.

[0184] It is desirable to avoid the addition of a material such assilica which tends to form glass, for the following reason. That is, thematerial such as silica is readily reacted with thepiezoelectric/electrostrictive material during the heat treatment forthe piezoelectric/electrostrictive layer 22. As a result, thecomposition is varied, and the piezoelectric characteristics aredeteriorated.

[0185] On the other hand, it is preferable that the pair of electrodes24, 26 of the piezoelectric/electrostrictive element 18 a, 18 b arecomposed of a metal which is solid at room temperature and which isexcellent in conductivity. It is possible to use, for example, metalsimple substances such as aluminum, titanium, chromium, iron, cobalt,nickel, copper, zinc, niobium, molybdenum, ruthenium, palladium,rhodium, silver, stannum, tantalum, tungsten, iridium, platinum, gold,and lead, and alloys thereof. Further, it is also preferable to use acermet material obtained by dispersing the same materials as those ofthe piezoelectric/electrostrictive layer 22 and/or the thin platesections 12 a, 12 b therein.

[0186] The material of the electrodes 24, 26 of thepiezoelectric/electrostrictive element 18 a, 18 b is selected anddetermined depending on the method for forming thepiezoelectric/electrostrictive layer 22. For example, when thepiezoelectric/electrostrictive layer 22 is formed by the sintering onthe electrode 24 after forming the first electrode 24 on the thin platesection 12 a, 12 b, it is necessary for the first electrode 24 to use ahigh melting point metal such as platinum, palladium, platinum-palladiumalloy, or silver-palladium alloy which does not change at the sinteringtemperature of the piezoelectric/electrostrictive layer 22. However, thesecond electrode 26, which is disposed at the outermost layer and whichis formed on the piezoelectric/electrostrictive layer 22 after formingthe piezoelectric/electrostrictive layer 22, can be formed as anelectrode at a low temperature. Therefore, it is possible to use a lowmelting point metal as a major component including, for example,aluminum, gold, and silver.

[0187] Each of the thicknesses of the electrodes 24, 26 may be a factorto considerably decrease the displacement of thepiezoelectric/electrostrictive element 18 a, 18 b. Therefore, especiallyfor the electrode to be formed after the sintering of thepiezoelectric/electrostrictive layer 22, it is preferable to use amaterial such as an organic metal paste with which a dense and thinnerfilm can be obtained after the sintering, including, for example, goldresinate paste, platinum resinate paste, and silver resinate paste.

[0188] The piezoelectric/electrostrictive device 10 according to thisembodiment can be preferably used for a variety of sensors including,for example, ultrasonic wave sensors, acceleration sensors, angularvelocity sensors, shock sensors, and mass sensors. Thepiezoelectric/electrostrictive device 10 according to this embodiment isfurther advantageous in that the sensitivity of the sensor can be easilyadjusted by appropriately adjusting the size of an object to be attachedbetween the end surfaces 32 a, 32 b or between the thin plate sections12 a, 12 b.

[0189] As for the method for forming the piezoelectric/electrostrictiveelement 18 a, 18 b on the surface of the ceramic laminate in the methodfor producing the piezoelectric/electrostrictive device 10, it ispossible to use the screen printing method described above as well as athick film formation method such as the dipping method, the applicationmethod, and the electrophoresis method and a thin film formation methodsuch as the ion beam method, the sputtering method, the vacuumdeposition, the ion plating method, the chemical vapor deposition method(CVD), and plating.

[0190] When the piezoelectric/electrostrictive elements 18 a, 18 b areformed by using any one of the film formation methods as describedabove, the piezoelectric/electrostrictive elements 18 a, 18 b and thethin plate sections 12 a, 12 b can be joined and arranged integrallywithout using any adhesive. It is possible to secure the reliability andthe reproducibility, and it is possible to facilitate the integrationthereof.

[0191] In the present embodiment, it is preferable that thepiezoelectric/electrostrictive elements 18 a, 18 b are formed by thethick film formation method, for the following reason. That is, when thethick film formation method is used especially for the formation of thepiezoelectric/electrostrictive layer 22, the film can be formed byusing, for example, a paste, a slurry, a suspension, an emulsion, or asol containing, as a major component, grains or powder of piezoelectricceramics having an average grain diameter of 0.01 to 5 μm, preferably0.05 to 3 μm. When the film obtained as described above is sintered, itis possible to obtain good piezoelectric/electrostrictivecharacteristics.

[0192] The electrophoresis method is advantageous in that the film canbe formed at a high density with a high shape accuracy. The screenprinting method is advantageous to simplify the production steps,because the film formation and the pattern formation can be performedsimultaneously.

[0193] The method of cutting the ceramic laminate includes mechanicalmachining such as dicing machining and wire saw machining as well aselectron beam machining and laser machining by using, for example, theYAG laser and the excimer laser.

[0194] When the ceramic substrate 16 is constructed, for example, asshown in FIG. 15, cutouts (cutaways) 200 are sometimes formed in thevicinity of the thin plate sections 12 a, 12 b respectively on the innerwall of the fixed section 14 (piezoelectric/electrostrictive device 10 aaccording to a modified embodiment). Accordingly, the lengths of thepair of thin plate sections 12 a, 12 b are substantially lengthened, andit is possible to obtain large displacement amounts. Further, the thinplate sections 12 a, 12 b are more flexible, and hence it is alsopossible to reduce the electric power consumption. The embodiment shownin FIG. 15 is illustrative of a state in which the first wiring pattern50 is formed to have approximately the same length as that of thestacked portion of the piezoelectric/electrostrictive element 18 a, 18 bwithout forming the first wiring pattern 50 up to the upper end of thethin plate section 12 a, 12 b.

[0195] However, it is feared that the stress may be concentrated on thejoined portions 202 between the thin plate sections 12 a, 12 b and themovable sections 20 a, 20 b and on the joined portions 204 between thethin plate sections 12 a, 12 b and the fixed section 14, and the shockresistance of the piezoelectric/electrostrictive device 10 a may bedeteriorated.

[0196] In view of the above, specified embodiments of the preferredstructure of the piezoelectric/electrostrictive device 10 according tothe embodiment of the present invention will be described below withreference to FIGS. 16 to 24.

[0197] As shown in FIG. 16, a piezoelectric/electrostrictive device 10Aaccording to a first specified embodiment is constructed inapproximately the same manner as the piezoelectric/electrostrictivedevice 10 a according to the modified embodiment shown in FIG. 15described above. However, the piezoelectric/electrostrictive device 10Aaccording to the first embodiment differs in that additional members206, each of which is based on a second material, are arranged at thejoined portions 202 between the thin plate sections 12 a, 12 b and themovable sections 20 a, 20 b and at the joined portions 204 between thethin plate sections 12 a, 12 b and the fixed section 14. Those usable asthe second material include metals and materials containing metals.

[0198] Usually, the ceramics have high breaking strength against thecompressive stress, but the breaking strength of the ceramics is lowagainst the tensile stress. On the other hand, the metal has the highbreaking strength against the tensile stress, but the metal tends to bedeformed, for example, bent by the compressive stress, and the strengthof the metal to maintain the shape is low against the compressivestress. However, the metal is not broken unlike the ceramics. In otherwords, the metal has such a property that the metal tends to cause theelastic deformation, and the amount of allowance of the elasticdeformation before causing the breakage is large as compared with theceramics. Therefore, when the two materials (ceramics and metal) arecombined, then it is possible to mutually supplement the drawbacks ofthe both, and it is possible to secure the high strength.

[0199] Further, when the metal is arranged on the surface, then themetal causes the elastic deformation in response to the tensile stress,and the metal absorbs the stress. Therefore, the fracture limitation israised, and the breaking strength is increased as compared with a casein which the ceramics is exposed to the surface. In particular, it ispossible to enhance the shock resistance.

[0200] In the first specified embodiment, the additional members 206 arearranged at the joined portions 202 between the thin plate sections 12a, 12 b and the movable sections 20 a, 20 b and at the joined portions204 between the thin plate sections 12 a, 12 b and the fixed section 14.Therefore, when the additional member 206 is composed of metal, it ispossible to obtain the function and the effect as described above. Thatis, the stress concentration is usually caused at the joined portions202, 204. However, when the additional member 206, which is softer thanthe ceramics, is expanded and contracted, then the shock, which isbrought about by the stress concentration, is absorbed, and it ispossible to enhance the shock resistance.

[0201] When the additional member 206 is composed of the metal having ahigh elastic modulus, it is advantageous to enhance the shock resistanceas described above. However, it is feared that the metal may beexfoliated from the ceramic substrate 16. Accordingly, the material forconstituting the additional member 206 is not limited to the metal asdescribed above. Alternatively, the additional member 206 may becomposed of a cermet containing metal. In this arrangement, there is nofear of exfoliation because of the high joining strength with respect tothe ceramics.

[0202] That is, the material for constituting the additional member 206is required to have the following characteristics. (1) The elasticmodulus is higher than that of the ceramics, similarly to the metal. (2)The coefficient of thermal expansion is approximate to that of theceramics which is the principal material for the ceramic substrate 16.(3) The adhesion strength (joining strength) with respect to theceramics is high. The material, which has the characteristics asdescribed above, may be exemplified by a cermet of metal and theconstitutive material (ceramics) of the ceramic substrate 16.

[0203] As for the metal, it is preferable to use noble metals such as Ptcapable of being co-fired together with the ceramics at a hightemperature. However, it is also allowable to use, for example,titanium, chromium, and nickel. Zirconia is preferred as the ceramics.

[0204] When the ratio of the metal in the cermet is low, then thejoining strength with respect to the ceramics is raised, but theproperty as the metal becomes poor. Therefore, it is impossible toexpect the improvement in strength so much. According to this fact, itis preferable to select a condition in which the ratio of the metal ishigh and it is possible to secure the joining strength with respect tothe ceramics. Therefore, the blending ratio of the cermet is such thatthe metal is preferably 0.5 to 1 and more preferably 0.7 to 0.9 providedthat the ceramics is 1 in volume ratio.

[0205] When the piezoelectric/electrostrictive device 10A including theadditional members 206 as described above is manufactured, it is enoughto add only a step of pattern-printing a cermet paste to be convertedinto the additional members 206 thereafter during the process formanufacturing the ceramic green laminate 58 as described above (see FIG.5).

[0206] That is, the green sheets corresponding to the thin platesections 12 a, 12 b are processed to have the predetermined shapes bythe method including, for example, the punching out based on the use ofa die or laser machining, and then patterns based on the cermet pastehaving a predetermined thickness are formed by using the screen printingat predetermined positions (positions corresponding to the joinedportions 202 between the thin plate sections 12 a, 12 b and the movablesections 20 a, 20 b and the joined portions 204 between the thin platesections 12 a, 12 b and the fixed section 14 in this embodiment) on thesurfaces (surfaces on which the pair of thin plate sections 12 a, 12 bare opposed to one another) to serve as the back surfaces of the thinplate sections 12 a, 12 b.

[0207] Methods other than the printing method may be also adopted. Thatis, patterns may be formed by spray by using masking, or a green sheetof cermet may be manufactured, followed by performing the punching outso that obtained pieces are stacked to form the additional members.

[0208] The thickness of the cermet paste is preferably 0.003 to 0.07 mmand more preferably 0.005 to 0.01 mm, for the following reason. That is,if the thickness is thinner than 0.03 mm, the effect to improve thebreaking strength is poor. If the thickness is thicker than 0.07 mm,then the entire thin plate section 12 a, 12 b is too thick, and aharmful influence is caused such that the displacement amount isdecreased. Therefore, it is preferable that the thickness of the ceramicportion at the portion for forming the cermet paste and the thickness ofthe cermet paste to be formed are appropriately adjusted to optimize thecharacteristics of the piezoelectric/electrostrictive device whiletaking the balance with the breaking strength into consideration.

[0209] The length for inserting the additional member 206 into thejoined portion 202, 204 (conveniently referred to as “insertion length”)La is preferably the thickness or more of the thin plate section 12 a,12 b (thickness of the ceramic portion), for the following reason. Thatis, if the insertion length La is too short, then the strict positioningaccuracy is required during the pattern printing and the lamination, andit is feared that the yield may be lowered.

[0210] Next, as shown in FIG. 17, a piezoelectric/electrostrictivedevice 10B according to a second specified embodiment is constructed inapproximately the same manner as the piezoelectric/electrostrictivedevice 10A according to the first specified embodiment shown in FIG. 16described above. However, the piezoelectric/electrostrictive device 10Baccording to the second specified embodiment differs in that additionalmembers 206 are arranged continuously along the back surfaces (surfaceson which the pair of thin plate sections 12 a, 12 b are opposed to oneanother) of the thin plate sections 12 a, 12 b over ranges from theupper ends of the movable sections 20 a, 20 b to the outer end surface14 a of the fixed section 14.

[0211] In this arrangement, it is possible to avoid breakage of theceramics (for example, any occurrence of cracks and fracture) whichwould be otherwise caused from the back surfaces of the thin platesections 12 a, 12 b, in addition to the function and the effect of thepiezoelectric/electrostrictive device 10A according to the firstspecified embodiment.

[0212] Next, as shown in FIG. 18, a piezoelectric/electrostrictivedevice 10C according to a third specified embodiment is constructed inapproximately the same manner as the piezoelectric/electrostrictivedevice 10B according to the second specified embodiment shown in FIG. 17described above. However, the piezoelectric/electrostrictive device 10Caccording to the third specified embodiment differs in that additionalmembers 206 are arranged continuously over ranges from the joinedportions 202 between the thin plate sections 12 a, 12 b and the movablesections 20 a, 20 b to the joined portions 204 between the thin platesections 12 a, 12 b and the fixed section 14.

[0213] In this arrangement, the ceramic substrate 16 is not completelydivided by the additional members 206, but the ceramic substrate 16 ispartially connected. Accordingly, an advantage is obtained such that theadditional members 206 are hardly exfoliated even by the stress caused,for example, by the difference in thermal expansion. Therefore, it ispossible to improve the reliability in relation to the thermal shocksuch as the quick heating and the quick cooling.

[0214] Next, as shown in FIG. 19, a piezoelectric/electrostrictivedevice 10D according to a fourth specified embodiment is constructed inapproximately the same manner as the piezoelectric/electrostrictivedevice 10C according to the third specified embodiment shown in FIG. 18described above. However, the piezoelectric/electrostrictive device 10Daccording to the fourth specified embodiment differs in that firstwiring patterns 50 of the piezoelectric/electrostrictive elements 18 a,18 b are formed to extend up to the upper ends of the thin platesections 12 a, 12 b respectively.

[0215] In this arrangement, it is possible to avoid the breakage of theceramics which would be otherwise caused from the front surfaces (sidesurfaces) of the thin plate sections 12 a, 12 b, in addition to the factthat it is possible to avoid the breakage of the ceramics (for example,any occurrence of cracks and fracture) which would be otherwise causedfrom the back surfaces of the thin plate sections 12 a, 12 b.

[0216] Next, as shown in FIG. 20, a piezoelectric/electrostrictivedevice 10E according to a fifth specified embodiment is constructed inapproximately the same manner as the piezoelectric/electrostrictivedevice 10D according to the fourth specified embodiment shown in FIG. 19described above. However, the piezoelectric/electrostrictive device 10Eaccording to the fifth specified embodiment differs in that secondadditional members 214 are arranged at approximately intermediateportions in the thickness direction of the respective thin platesections 12 a, 12 b respectively. Constitutive materials, which areequivalent to those of the additional members 206, can be used for thesecond additional members 214.

[0217] In this arrangement, the second additional members 214 composedof metal or the like are inserted into the approximately intermediateportions in the thickness direction of the thin plate sections 12 a, 12b. Therefore, the second additional members 214 bring about the functionand the effect which are similar to those brought about by thereinforcing rods of the reinforced concrete of the building. Thus, it ispossible to further enhance the strength.

[0218] Next, as shown in FIG. 21, a piezoelectric/electrostrictivedevice 10F according to a sixth specified embodiment is constructed inapproximately the same manner as the piezoelectric/electrostrictivedevice 10C according to the third specified embodiment shown in FIG. 18described above. However, the piezoelectric/electrostrictive device 10Faccording to the sixth specified embodiment differs in that the forwardend portions of the thin plate sections 12 a, 12 b are not thick-walledand the thicknesses of the forward end portions are approximately thesame as the thicknesses of intermediate portions of the thin platesections 12 a, 12 b and that additional members 206 are formed at onlythe joined portions 204 between the thin plate sections 12 a, 12 b andthe fixed section 14. In this arrangement, the opposing surfaces of theforward end portions of the thin plate sections 12 a, 12 b function asattachment surfaces 34 a, 34 b for an object.

[0219] According to this arrangement, no thick-walled portion exists atthe forward end portions of the thin plate sections 12 a, 12 b, and thestress concentration is scarcely caused. Therefore, it is possible toimprove the shock resistance.

[0220] Next, as shown in FIG. 22, a piezoelectric/electrostrictivedevice 10G according to a seventh specified embodiment is constructed inapproximately the same manner as the piezoelectric/electrostrictivedevice 10F according to the sixth specified embodiment shown in FIG. 21described above. However, the piezoelectric/electrostrictive device 10Gaccording to the seventh specified embodiment differs in that additionalmembers 206 are formed to extend along the back surfaces of the thinplate sections 12 a, 12 b up to portions in the vicinity of theattachment surfaces 34 a, 34 b. In this arrangement, it is possible toavoid the breakage of the ceramics (for example, any occurrence ofcracks and fracture) which would be otherwise caused from the backsurfaces of the thin plate sections 12 a, 12 b in addition to thefunction and the effect of the piezoelectric/electrostrictive device 10Faccording to the sixth specified embodiment.

[0221] Next, as shown in FIG. 23, a piezoelectric/electrostrictivedevice 10H according to an eighth specified embodiment is constructed inapproximately the same manner as the piezoelectric/electrostrictivedevice 10G according to the seventh specified embodiment shown in FIG.22 described above. However, the piezoelectric/electrostrictive device10H according to the eighth specified embodiment differs in thatadditional members 206 are formed continuously along the back surfacesof the thin plate sections 12 a, 12 b over ranges from the forward endsof the thin plate sections 12 a, 12 b to the outer end surface 14 a ofthe fixed section 14 and the first wiring patterns 50 are formed toextend up to the forward ends of the thin plate sections 12 a, 12 b andthat distinct cutouts 220 are formed at portions of the outer endsurface 14 a of the fixed section 14 corresponding to the cutouts 200formed on the inner wall of the fixed section 14.

[0222] In this arrangement, it is possible to increase the displacementamounts of the forward end portions of the thin plate sections 12 a, 12b. However, it is feared that any exfoliation may be caused, because theconnecting portions between the fixed section 14 and the thin platesections 12 a, 12 b are small in area. Accordingly, the exfoliation ofthe thin plate sections 12 a, 12 b can be effectively avoided by fillingthe distinct cutouts 220 with a resin 222 as shown by hatched lines inFIG. 23.

[0223] The length of the piezoelectric/electrostrictive element 18 a, 18b (length along the thin plate section 12 a, 12 b) may be short as inthe piezoelectric/electrostrictive devices 10A to 10H according to thefirst to eight specified embodiments shown in FIGS. 16 to 23.Alternatively, as illustrated by a piezoelectric/electrostrictive device101 according to a ninth specified embodiment shown in FIG. 24, thelength of the piezoelectric/electrostrictive element 18 a, 18 b may belengthened so that first end surfaces 226 of the respectivepiezoelectric/electrostrictive elements 18 a, 18 b are disposed atapproximately the same positions as those of first end surfaces 228 ofthe movable sections 20 a, 20 b respectively.

[0224] The piezoelectric/electrostrictive devices 10, 10 a, 10A to 10Idescribed above are usable as various transducers, various actuators,frequency region functional parts (filters), transformers, and activedevices including, for example, vibrators, resonators, oscillators, anddiscriminators for communication and power generation as well as sensordevices including, for example, ultrasonic sensors, accelerationsensors, angular velocity sensors, shock sensors, and mass sensors. Inparticular, the piezoelectric/electrostrictive devices 10, 10 a, 10A to10I described above are preferably usable for various actuators to beused for mechanisms for adjusting the angle and adjusting thepositioning and the displacement of, for example, various precisionparts such as optical instruments and precision instruments.

[0225] As explained above, the following effects are obtained by thepiezoelectric/electrostrictive device according to the present inventionand the method of manufacturing the same.

[0226] (1) It is possible to increase the occupied area of a conductiveportion in one electrode layer, and it is possible to increase thedriving force, improve the yield, and realize the easy control.

[0227] (2) It is possible to effectively reduce the volume of apiezoelectric/electrostrictive element itself to decrease the resistanceon the displacement action, and it is possible to further increase thedriving force (increase the displacement amount).

[0228] (3) It is possible to prevent a piezoelectric/electrostrictiveelement formed on a ceramic substrate from exfoliation, it is possibleto reduce the number of steps in relation to the production of thepiezoelectric/electrostrictive device, it is possible to improve thethroughput, and it is possible to avoid the deterioration of function ofthe piezoelectric/electrostrictive device.

[0229] (4) It is possible to improve the shock resistance by increasingthe breaking strength and it is possible to provide apiezoelectric/electrostrictive device which has high reliability.

What is claimed is:
 1. A piezoelectric/electrostrictive devicecomprising a ceramic substrate and at least apiezoelectric/electrostrictive element stacked on said ceramicsubstrate, wherein said piezoelectric/electrostrictive element includesa plurality of piezoelectric/electrostrictive layers and a plurality ofelectrode layers stacked alternately in a comb like structure on saidceramic substrate, said electrode layers include one or moreintermediate electrode layers at an intermediate portion of saidpiezoelectric/electrostrictive element, said intermediate electrodelayers include metal electrode layers interposed between saidpiezoelectric/electrostrictive layers and cermet electrode layers notinterposed between said piezoelectric/electrostrictive layers, and saidmetal electrode layers and said cermet electrode layers are connected toone another.
 2. The piezoelectric/electrostrictive device according toclaim 1, wherein said metal electrode layers are thinner than saidcermet electrode layers.
 3. The piezoelectric/electrostrictive deviceaccording to claim 1, wherein one or more gaps of one or more lowerelectrode layers positioned at a lower portion of saidpiezoelectric/electrostrictive element are formed on said ceramicsubstrate and are filled with an insulating layer.
 4. Thepiezoelectric/electrostrictive device according to claim 1, wherein oneor more upper electrode layers provided at an upper portion of saidpiezoelectric/electrostrictive element are formed by depositing a filmof resinate of a conductive material to said upper portion.
 5. Apiezoelectric/electrostrictive device comprising a ceramic substrate anda piezoelectric/electrostrictive element formed on said ceramicsubstrate, wherein said ceramic substrate includes fixed sections whichhave a large thickness and a pair of thin plate sections which areformed continuously from said fixed section and which are thinner thansaid fixed sections; and second material is used between said pair ofthin plate sections and said fixed sections.
 6. Thepiezoelectric/electrostrictive device according to claim 5, wherein saidsecond material is a metal.
 7. The piezoelectric/electrostrictive deviceaccording to claim 5, wherein said second material is a cermet.
 8. Thepiezoelectric/electrostrictive device according to claim 5, wherein saidsecond material is a cermet comprising said ceramic substrate and ametal.
 9. The piezoelectric/electrostrictive device according to claim5, wherein said piezoelectric/electrostrictive element is arranged atone or more thin plate sections of said pair of thin plate sections. 10.A piezoelectric/electrostrictive device comprising a ceramic substrateand a piezoelectric/electrostrictive element formed on said ceramicsubstrate, wherein said ceramic substrate includes fixed sections whichhave a large thickness, a pair of thin plate sections which are formedcontinuously from said fixed sections and which are thinner than saidfixed sections, and movable sections which are provided at ends of saidpair of thin plate sections; and second material is used between saidpair of thin plate sections and said fixed sections and between saidpair of thin plate sections and said movable sections.
 11. Thepiezoelectric/electrostrictive device according to claim 10, whereinsaid second material is used over ranges from between said pair of thinplate sections and said fixed sections to between said pair of thinplate sections and said movable sections.
 12. Thepiezoelectric/electrostrictive device according to claim 10, whereinsaid second material is a metal.
 13. The piezoelectric/electrostrictivedevice according to claim 10, wherein said second material is a cermet.14. The piezoelectric/electrostrictive device according to claim 10,wherein said second material is a cermet comprising said ceramicsubstrate and a metal.
 15. The piezoelectric/electrostrictive deviceaccording to claim 10, wherein said piezoelectric/electrostrictiveelement is arranged at one or more thin plate sections of said pair ofthin plate sections.
 16. A method for producing apiezoelectric/electrostrictive device comprising a ceramic substrate anda piezoelectric/electrostrictive element formed on said ceramicsubstrate, said method including: a step for manufacturing said ceramicsubstrate by sintering a molding after forming said molding by using rawmaterials containing a ceramic material; and a step for forming saidpiezoelectric/electrostrictive element by a plurality ofpiezoelectric/electrostrictive layers and a plurality of electrodelayers stacking alternately in a comb like structure on said ceramicsubstrate, wherein said step for forming saidpiezoelectric/electrostrictive element includes a step for forming oneor more intermediate electrode layers at an intermediate portion of saidpiezoelectric/electrostrictive element by sintering a cermet filmcontaining a conductive material and a piezoelectric/electrostrictivematerial to form said intermediate electrode layers.
 17. The method forproducing said piezoelectric/electrostrictive device according to claim16, wherein said step for forming said piezoelectric/electrostrictiveelement includes a step for filling one or more gaps of one or morelower electrode layers positioned at a lower portion of saidpiezoelectric/electrostrictive element with an insulating layer to formsaid lower electrode layers.
 18. The method for producing saidpiezoelectric/electrostrictive device according to claim 17, whereinafter a first cermet to be converted into said lower electrode layersand a second cermet to be converted into said insulating layer areformed on said ceramic substrate by printing respectively, said firstand second cermets formed on said ceramic substrate by printing aresintered.
 19. A method for producing a piezoelectric/electrostrictivedevice comprising a ceramic substrate including fixed sections whichhave a large thickness and a pair of thin plate sections which areformed continuously from said fixed sections and which have a thinthickness, and a piezoelectric/electrostrictive element formed on saidceramic substrate, said method including: a step for forming a cermetpaste by printing on opposing surfaces of a plurality of ceramic greensheets to be converted into said thin plate sections; a step forlaminating said plurality of ceramic green sheets to form a ceramicgreen laminate; a step for sintering said ceramic green laminate to forma ceramic laminate; and a step for cutting off unnecessary portionsafter forming and sintering said piezoelectric/electrostrictive elementon said ceramic laminate to manufacture saidpiezoelectric/electrostrictive device in which a second material is usedbetween said pair of thin plate sections and said fixed sections.